This proposal is a competing renewal which aims to better understand why infection, which is common after stroke, negatively impacts outcome. Our research demonstrates that an immune response to central nervous system (CNS) antigens occurs after stroke and that the nature of this immune response depends upon the experimental conditions and affects neurological outcome. Specifically, Lewis rats that develop a TH1 type immune response to brain antigens experience worse outcome while Lewis rats that develop a regulatory type response (TREG) experience better outcome. The predisposition to developing a TH1 response is increased by systemic inflammation induced with lipopolysaccharide (LPS). We believe that this model may help to explain why patients who develop an infection following stroke experience worse outcome. The goals of the current project are to assess the "clinical relevance" of our model by validating our findings using a true infection model. We further aim to better define the nature and regulation of this post-ischemic immune response and assess the effect of antibiotic therapy and the role of the sympathetic nervous system on this response. The primary hypothesis to be addressed in the research outlined is: does systemic infection in the immediate post-stroke period increase the likelihood of developing a detrimental autoimmune response to CNS antigens? PUBLIC HEALTH RELEVANCE: Infection is common after stroke and is associated with worse outcome. It is possible that this detrimental effect is mediated by the development of an autoimmune response to brain, and as such, could be modulate to improve outcome.